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Broken Back?

Broken Back?. A smokejumper (mass = 70 kg) hits the ground with 25x body weight. If the load is concentrated on the facet joints, which have an area of 1 cm 2 , will they break ? (F = mass x g; g = 9.81 m/s 2 ) Yes No It depends …. Broken Back?.

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Broken Back?

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  1. Broken Back? A smokejumper (mass = 70 kg) hits the ground with 25x body weight. If the load is concentrated on the facet joints, which have an area of 1 cm2, will they break? (F = mass x g; g = 9.81 m/s2) • Yes • No • It depends …

  2. Broken Back? A smokejumper (mass = 70 kg) hits the ground with 25x body weight. If the load is concentrated on the facet joints, which have an area of 1 cm2, will they break? (F = mass x g; g = 9.81 m/s2) Given: F = 25 x mass x g F = 25 x 70kg x 9.81m/s2 = 17167.5 N A = 1 cm2 Stress=F/A A = (1 cm2)(1 m/100 cm)(1 m/100 cm) A = 0.0001 m2 = 1 x 10-4 m2 Stress = F(N)/A(m2) = 171675000 = 171.675 MPa Bone Ultimate Stress = 190 MPa (Compression) 171.675 MPa < 190 MPa Below limit : NO will not break

  3. Good Vibrations

  4. Good Vibrations Small, subtle vibrations reduce bone loss in laboratory animals.

  5. Good Vibrations Small, subtle vibrations reduce bone loss in laboratory animals.

  6. http://www.marodyne.com/research/

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